Abstract: Experimental research and theoretical analysis have been carried out by means of a C0₂ laser as the radiation source to heat the test samples at atmospheric pressure and temperature. The ignition delay of each of the test isamples was measured as a function of radiation intensity. According to the experimental observation and theoretical analysis,a comprehensive model of ignition for composite solid pro-pellant is established which tikes into account the effects of the gas-phase reaction, the oxilizer release, the hetergeneous reaction and the polymer fuel pyrolysis in the depth of the propellant. The results of theoretical analysis come to quite a good agreement with the corresponding experimental data. Both experimental and computational results show that the ignition delay decreases with increasing radiant heat flux. The minimum and the optimum values of heat flux appear to exist. The criterion of ignition is deduced.